The present invention relates generally to a high power, high frequency transformer, and more particularly to a transformer with a non-integer turns ratio.
There is a need for non-integer turns ratio transformers, particularly in impedance matching and even more particularly in combiners where a .sqroot.3 or .sqroot.5 turns ratio is desired. Such non-integer turns ratio transformers are generally difficult to physically construct, often requiring numerous manufacturing steps difficult to automate.
There is also a need for a defined pass band over a specific frequency range, a need generally satisfied by a filter following the transformer. Improved efficiency results from combining the transformer and filter functions in a single unit.
In addition, there are many environments where vibration presents structural problems, particularly for magnetic cored, liquid cooled transformers.
These and other problems occur, by way of example, in modern shipboard solid state radio transmitters where transformers may be used to construct combiners for summing the power of two or more radio frequency sources to a single antenna. Because it has desirable magnetic characteristics, i.e., low reluctance, ferrite is typically used for the core of such transformers, generally as a toroid or a block with holes for the windings drilled therein. For high power (1 to 100 kw) applications, however, ferrite cores reach sufficient magnetic flux that the application of a linear current to the primary winding will not result in a linear magnetic induction without prohibitive amounts of ferrite making the transformer unacceptably expensive, bulky, heavy and susceptible to vibration damage.
Where non-integer turn ratios are desired, e.g., 1.73 (.sqroot.3) and 2.24 (.sqroot.5), multi-filar windings on ferrite cores have been used, but are structurally complicated and therefore difficult and expensive to build.
Furthermore, the use of ferrite for high power applications, produces severe eddy current and hysteresis losses reflected by heat dissipation in the transformer core. Such losses limit maximum transformer power, and may require elaborate and potentially hazardous cooling systems to offset the temperature rise of the ferrite. These problems are particularly severe in shipboard environments which are sensitive to both size and weight considerations, where the available electric power is limited, and where a cored transformer and its liquid cooling systems are highly susceptible to shock and vibration.
It is accordingly an object of the present invention to obviate many of the above problems of the known prior art and to provide a novel high power, high frequency transformer.
Another object of the present invention is to provide a novel high power, high frequency transformer that is simple in construction, light in weight and low in cost.
Still another object is to provide a novel high power, high frequency transformer with significantly improved resistance to shock and vibration.
Yet another object of the present invention is to provide a novel high power, high frequency transformer with a non-integer turns ratio.
A further object of the present invention is to provide a novel transformer having significant harmonic and intermodulation product suppression.
Another object of the present invention is to provide a novel high frequency, high power transformer that has bandpass characteristic that is substantially independent of temperature at normal operating ranges.
Yet still another object of the present invention is to provide a novel method of transforming impedance by a non-integer factor.
It is still a further objective to obtain a novel transformer having a bandwidth ratio up to 5:1.